Active muffler for an exhaust system

ABSTRACT

An active muffler ( 1 ) for an exhaust system ( 2 ) of an internal combustion engine has a first space ( 3 ) and a second space ( 4 ) that is separated from the former via a partition ( 5 ). The partition ( 5 ) has a wall opening ( 6 ) into which is inserted an electronic sound absorber ( 7 ) having a chassis ( 8 ) and a diaphragm ( 9 ). During operation, the electronic sound absorber directs anti-sound toward the first space ( 3 ) and thereby reduces the sound emission generated by the exhaust system ( 2 ). The chassis ( 8 ) of the electronic sound absorber ( 7 ) and the partition ( 5 ) are made in one piece.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a and claims the benefit of priority under 35 U.S.C. §119 of German Patent Application 10 2006 010 558.3 filed Mar. 6, 2007, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an active muffler for an exhaust system of an internal combustion engine, in particular in a motor vehicle.

BACKGROUND OF THE INVENTION

Because of steadily increasing demands with regard to noise emission by exhaust systems, in recent years there has been increased use of exhaust systems having so-called active noise control by anti-sound (destructive interference sound). The function is based on extinction of two superimposed sound signals. To do so, a synthetically generated signal in phase opposition (anti-sound), usually emitted by loudspeakers, is superimposed on the interfering sound of the exhaust system so as to result in the most extensive possible extinction of the interfering signal. These active mufflers are used not only in the exhaust systems of internal combustion engines but also in the ventilation ducts of air conditioning systems. One advantage of these active systems is their size, which requires much less installation space in comparison with passive systems such as mufflers. This is true in particular in the area of low frequencies because this is where conventional mufflers assume a large size. In addition, active systems are much more flexible and can adapt to altered operating conditions, e.g., different rotational speeds or different engine noises, to some extent automatically.

SUMMARY OF THE INVENTION

The present invention relates to the problem of providing an improved embodiment for an active exhaust muffler that is characterized in particular by a simple design.

According to the invention, an active muffler is provided for an exhaust system of an internal combustion engine, in particular of an internal combustion engine. The active muffler comprises a muffler body structure as well as a partition defining a first muffler space, into which sound transported in the exhaust system can enter in the muffler body structure, and a second muffler space in said muffler body structure. An electronic sound absorber is provided comprising a chassis and a diaphragm. The electronic sound absorber generates sound directed at the first muffler space for canceling some of the sound transported in the exhaust system. The chassis and the partition are made in one piece.

With an active muffler for an exhaust system of an internal combustion engine, the present invention is based on the general idea of integrating a chassis of an electronic sound absorber, i.e., an anti-sound generator, into a partition between a first space and a second space. Airborne sound transported in the exhaust system can enter the first space, and the electronic sound absorber installed in (extending into) the second space can act upon the first space by absorbing sound electronically through a wall opening in the partition. The fact that the chassis of the electronic sound absorber and the partition are made in one piece greatly simplifies the installation of the active muffler and thereby helps to reduce installation costs. At the same time, a one-piece design of the chassis of the partition is easily possible in the partition manufacturing process by shaping the chassis or at least parts thereof out of the partition by punching and bending. In the chassis formed in this way, the electronic sound absorber may be used in another processing step, wherein its diaphragm is connected at one end to a circumferential edge of the wall opening and at the other end to a sound generator of the electronic sound absorber. The partition prefabricated in this way can then be installed in the muffler without first having a complex installation, e.g., with screw connection of the chassis of the electronic sound absorber to the partition in assembly of the muffler. At the same time it is possible through the inventive design to save on fastening means such as screws as well as the damping elements, for example, which should provide a dampened bearing of the chassis on the partition.

In an advantageous embodiment, the partition with the diaphragm and/or with the chassis separates the first space from the second space in an airtight manner. This ensures that the second space and thus the electronics of the electronic sound absorber installed therein cannot come in contact with the chemically corrosive exhaust gases and therefore the long life of the inventive muffler can be increased.

The electronic sound absorber is expediently a loudspeaker. In this case, the electrodynamic loudspeakers that are generally used may also be used here; they can be manufactured inexpensively while also ensuring reliable sound suppression by emission of signals that are superimposed on the interfering waves. The loudspeakers are preferably adapted to the sound frequencies frequently occurring with the particular exhaust system and are designed for silencing these frequencies.

In another advantageous embodiment of the inventive approach, the partition and the electronic sound absorber are designed as a module that can be prefabricated. This allows a separation of the process of installation of the inventive muffler into prefabrication of the aforementioned module and a subsequent final installation of the muffler. Prefabrication of the module can be handled by a supplier because the module manufacturing process and the muffler manufacturing process can be carried out separately from one another.

Additional important features and advantages of the present invention are derived from the subclaims, the drawing and the respective description of the figures on the basis of the drawing.

It is self-evident that the features mentioned above and those yet to be explained below may be used not only in the particular combination given but also in other combinations or alone without going beyond the scope of the present invention.

A preferred exemplary embodiment of the invention is illustrated in the drawing and explained in greater detail in the following description. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is the only figure and shows a greatly simplified schematic longitudinal section through a part of an active muffler according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, according to FIG. 1, an active muffler 1 is provided for an exhaust system 2, only a portion of which is shown. The active muffler 1 is for an internal combustion engine. The muffler includes a housing 11 and comprises at least a first space 3 and a second space 4. Airborne sound conveyed in the exhaust system 2 may enter the first space 3 and may cause an unpleasant noise burden, depending on the frequency and loudness. Between the first space 3 and the second space 4 there is a partition 5 having a wall opening 6 into which an electronic sound absorber 7 is inserted according to FIG. 1. The wall opening 6 is completely sealed by the electronic sound absorber 7.

The arrangement of the first space 3 and/or the second space 4 according to FIG. 1 should merely represent one possible embodiment, but other embodiments, e.g., with additional spaces and/or noise obstacles such as additional partitions, baffles and the like may also be employed without departing from the present invention.

The electronic sound absorber 7 has, as shown in FIG. 1, a chassis 8 and a diaphragm 9, whereby the chassis 8 is preferably designed to accommodate electric or electronic components of the electronic sound absorber 7, e.g., an actuator or a sound generator that serves to drive the diaphragm 9. The diaphragm 9 of the electronic sound absorber 7 is preferably made of a material that is insensitive to temperature, e.g., a metal and is therefore especially suitable for use in exhaust systems 2 owing to the high temperatures prevailing there. As shown in FIG. 1, the electronic sound absorber 7 is set up in the second space 4 and is thus inserted into the wall opening 6 it the partition 5 in such a way that it can act upon the first space 3 with anti-sound during operation. To simplify the assembly of the active muffler 1 and thereby be able to implement it less expensively, the chassis 8 of the electronic sound absorber 7 and the partition 5 are manufactured in one piece. Such an inventive one-piece design of the chassis 8 and the partition 5 offers the great advantage that the chassis 8 and the partition 5 may essentially be manufactured in one operation, thereby avoiding later assembly of the chassis 8 on the partition 5.

The diaphragm 9 is designed to be airtight and is inserted into the wall opening 6 in such a way that it is in airtight connection with a circumferential edge of the wall opening 6. The chassis 8 itself may also be designed to be largely airtight with respect to the second space 4. The component formed from the partition 5 and the chassis 8 thus separates the first space 3 from the second space 4 in an airtight manner. Likewise, an interior space 12 is enclosed in an airtight manner by the chassis 8 in a diaphragm 9. Such an airtight separation is required to keep chemically corrosive exhaust gases that might be present in the first space 3, for example, away from the sensitive electronics of the electronic sound absorber 7. The airtight separation of the second space 4 from the first space 3 also results in the second space 4 having a sealed gas volume and thereby permitting an acoustic separation of the first space 3 from the second space 4 which is required for generating a sound pressure due to the vibration of the diaphragm 9.

The electronic sound absorber 7 is preferably designed as a loudspeaker and generates sound vibrations whose vibration phase is shifted by 180° in comparison with the vibration phase of the original wave generated in the exhaust system 2. When the phase-shifted sound wave encounters the original wave, the two waves advantageously cancel out one another, which is also referred to as destructive interference. Since the original wave is canceled, noise emission by the exhaust system 2 is reduced, which is a great advantage due to the increasingly strict noise emission requirements for exhaust systems 2 in particular. An electronic sound absorber 7 designed as a loudspeaker can be manufactured inexpensively and is adapted to the sound frequencies and amplitudes occurring in the exhaust system 2 with regard to its sound emission capability so that the greatest possible destructive interference can be ensured.

Due to the inventive method of designing the chassis 8 of the electronic sound absorber 7 as an integral component of the partition 5, it is also possible to design the partition 5 and the electronic sound absorber 7 as a prefabricated module which can be manufactured separately from the manufacturing process of the active muffler 1. Final assembly of the active muffler 1 may thus be performed more easily and more quickly and therefore also less expensively because the partition 5 with the integrated electronic sound absorber 7 as a completely prefabricated module need be connected only to the remainder of the active muffler 1 and/or to other parts of the exhaust system 2; furthermore, the connection of the chassis 8 to the partition 5, which is complex and therefore expensive but would otherwise be necessary during the fabrication of the active muffler 1, can now be omitted. In the case of a shell design of the housing 11, it is conceivable for the partition 5 to close a shell 10 of the active muffler 1 and/or to form a shell part of the muffler 1. A connection of the partition 5 to other components of the muffler 1, e.g., to the housing 1 and/or to the shell 10, can then be accomplished in the usual manner, e.g., via welding or flanging or folding.

Through the inventive method, it is thus possible to manufacture the chassis 8 and the partition 5 preferably in one operation, e.g., by means of a punching tool, so that only the electric or electronic parts of the electronic sound absorber 7 and the diaphragm 9 of the electronic sound absorber 7 sealing the wall opening 6 in the partition 5 need be installed subsequently. A general installation of the electronic sound absorber 7 and/or its chassis 8 on the partition 5 with the associated installation cost and the associated installation materials, e.g., screws and gaskets may thus be eliminated, which thus makes the installation much simpler and also allows the cycle times to be increased. Furthermore, it is a particularly great advantage that the fabrication of the partition 5 together with the integrated chassis 8 and/or the electronic sound absorber 7 may be performed separately from the fabrication of the active muffler 1 and therefore isolated from the actual manufacturing process of the active muffler 1.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 

1. An active muffler for an exhaust system of an internal combustion engine, the active muffler comprising: a first space into which airborne sound transported in the exhaust system can enter; an electronic sound absorber having a chassis and a diaphragm, said electronic sound absorber being situated in a second space of the muffler and acting upon said first space with anti-sound through a wall opening during operation; wherein said wall opening is designed in a partition that separates said second space from said first space; wherein the chassis of the electronic sound absorber and the partition are made in one piece.
 2. A muffler according to claim 1, wherein: the partition with the diaphragm and/or with the chassis separates the first space from the second space in an airtight manner.
 3. A muffler according to claim 1, wherein: the second space has a sealed gas volume.
 4. A muffler according to claim 1, wherein: said electronic sound absorber is a loudspeaker.
 5. A muffler according to claim 1, wherein: the partition seals a shell of the muffler assembled in the shell design.
 6. A muffler according to claim 1, wherein: the partition is connected to additional components of the muffler by one of welding and flanging.
 7. A muffler according to claim 1, wherein: the partition and the electronic sound absorber are designed as prefabricated modules.
 8. An active muffler for an exhaust system of an internal combustion engine, the active muffler comprising: a muffler body structure; a partition defining a first muffler space in said muffler body structure, said first muffler space being in fluid communication with the exhaust system whereby sound transported in the exhaust system can enter and said partition defining a second muffler space in said muffler body structure; an electronic sound absorber comprising a chassis and a diaphragm, said electronic sound absorber generating sound directed at said first muffler space for canceling some of the sound transported in the exhaust system, said chassis being formed integral with said partition.
 9. A muffler according to claim 8, wherein said partition in cooperation with at least one of said diaphragm and said chassis define an airtight barrier between said first muffler space and said second muffler space.
 10. The muffler according to claim 8, wherein said second space is a sealed gas volume defined by said muffler body structure and said partition.
 11. The muffler according to claim 8, wherein said electronic sound absorber comprises a loudspeaker.
 12. The muffler according to claim 8, wherein said muffler body structure is a shell structure and said partition seals a shell portion of a shell structure.
 13. The muffler according to claim 8, wherein said muffler body structure comprises a first shell part with a flange and a second shell part with a flange wherein the partition with integral chassis is connected between said first shell part flange and said second shell part flange.
 14. The muffler according to claim 8, wherein said partition with integral chassis is a prefabricated module and said electronic sound absorber is comprised of another prefabricated module.
 15. An motor vehicle muffler comprising: a muffler housing body with a first body component and a second body component; a single piece partition and chassis part connected to said first body component and said second body component and cooperating with said first body component and said second body component to define a first muffler space in fluid communication with an exhaust gas conduit carrying an exhaust gas stream of an internal combustion engine, whereby sound transported in the exhaust gas enters said first muffler space, and said partition and chassis part cooperating with said first body component and said second body component to define a second muffler space in said muffler housing body; an electronic sound absorber diaphragm mounted to said partition and chassis part, said electronic sound absorber generating sound directed at said first muffler space for canceling some of the sound transported in the exhaust gas.
 16. A muffler according to claim 15, wherein said single piece partition and chassis part and said diaphragm cooperate to define an airtight barrier between said first muffler space and said second muffler space, wherein said second space is a sealed gas volume.
 17. The muffler according to claim 16, wherein said electronic sound absorber comprises a loudspeaker with said chassis forming a portion thereof.
 18. The muffler according to claim 16, wherein said first body component is a shell structure and said second body component is a shell structure.
 19. The muffler according to claim 18, wherein said first body component includes a flange and said second body component includes a flange wherein said single piece partition and chassis part is connected between said first body component flange and said second body component flange.
 20. The muffler according to claim 15, wherein said single piece partition and chassis part is a prefabricated module. 